The present invention relates to an electromagnetic motor for a timepiece, the motor including a stator which comprises a cylindrical coil, a core traversing the coil, two pole pieces respectively in contact with the ends of the core, and a rotor arranged between the pole pieces.
The drawback in motors of the above mentioned type in that the median plane of the pole pieces does not pass through the axis of the core, that is to say through the axis of the coil, the pole pieces being applied against or under the ends of the core. Hence, if one does not desire the movable elements of the movement, such as the rotor of the motor and the gearing to go beyond the top of the coil, there is on one side of the pole pieces only a space which is smaller than half the thickness of the coil.
There has suggested for removing this drawback an arrangement according to which the ends of the core traversing the coil are each provided with a notch. The ends of the pole pieces in contact with the core are each provided with a notch, and the assembling of the core and the pole pieces being effected by reciprocal engagement of the notched portions.
However, the drawback of such arrangement is that at the place a location of these notches, the section of the core is lower than the section of saturation so that the notch produces an increase in the resistance to the passage of the magnetic flux.
The purpose of the present invention is to furnish a construction in which the median plane of the pole pieces is closer to the axis of the core of the coil than in the conventional construction without, however, the connection between the ends of the core and the pole pieces producing an increase of the resistance to the passage of the magnetic flux.